The present invention relates to a motor vehicle with a telescopic lift arm and, particularly to motor vehicles in which the telescopic lift arm, when operated at the front of the vehicle, is below the line of sight of the driver of the vehicle. Conventionally, such a lowered position corresponds to an all-round visibility of the driver in the cab.
As is known, to be able to lower the telescopic lift arm without restricting the line of sight of the driver, solutions have been adopted in which the vehicle engine is located on a first longitudinal side of the vehicle while the cab is located on a second longitudinal side, opposite to the first. The lift arm is lowered into a central recess formed in the vehicle body between the cab and the engine. The hydraulic assembly powering the telescopic arm is normally located at the rear of the vehicle. It will be appreciated that the central position of the telescopic arm and the hydraulic assembly powering the arm provides for a perfect load balance when operating the arm.
One of the problems posed by this type of vehicle is that the engine positioned on the lateral side of the cab must, for construction reasons, be located higher than the propeller shafts transmitting motion to the front and rear axles. With respect to the ground, the engine in fact is located at substantially the same height as the driver's cab, while the propeller shafts are traditionally located beneath the level of the cab. The main reason for this kind of arrangement lies in the fact that the engine and the device for transmitting motion from the engine to the universal joints of the propeller shafts having to be located substantially higher than the two propeller shafts to avoid being damaged when traveling over rough ground.
The above arrangement therefore poses the problem of providing a reliable system for transmitting motion between shafts--the output drive shaft of the engine and the propeller shafts--located at two different heights with respect to the ground. In addition, such a transmission system must also be located substantially beneath the recess in the vehicle body for receiving the telescopic arm in the lowered position.
One attempt to solve the above problem is described in U.S. Pat. No. 5,478,192, in which a motor vehicle is discussed having a telescopic lift arm, and wherein the cab and engine are located conventionally on opposite sides of the longitudinal axis of symmetry of the vehicle. A system for transmitting motion between the drive shaft coming out of the engine transmission and the propeller shafts is provided comprising two chains arranged in series. An inherent problem of such an arrangement is the creation of vibrations during drive transmission, and a poor reliability of the system as a whole. Moreover, in as much as the motion transfer case containing the chains sits on top of the engine transmission, the resultant overall length of the combined engine/transmission structure necessitates to spread the front and rear axles strongly apart, which badly influences the maneuverability of the vehicle.
Moreover, to get under the side member of the vehicle, the above system calls for dividing the motion transfer case into two chain housings inclined at an angle with respect to each other.